1. Field of the Invention
The present invention relates to a tilt sensor.
2. Description of the Related Art
FIGS. 9 and 10 depict an example of a conventional tilt sensor (see Japanese Laid-open Patent Publication No. 2007-139643). The illustrated tilt sensor X includes a substrate 91, a housing 92, a cover 93, a pair of photodetectors 94A, 94B, a light emitting element 95, and a rolling element 96. (The cover 93 is omitted in FIG. 10.) The pair of photodetectors 94A, 94B and the light emitting element 95 are mounted on a surface of the substrate 91, and enclosed in the housing 92. The housing 92 and the cover 93 define a hollow portion or space 92a. The hollow portion 92a is of such a shape that permits light from the light emitting element 95 to enter the space, and that causes the light reflected by the housing 92 to reach the photodetectors 94A, 94B. The hollow portion 92a contains the rolling element 96. The rolling element 96 is of a circular column shape, and free to roll inside the hollow portion 92a along the xy-plane. The lower surface of the substrate 91 is formed with terminals for surface mounting of the tilt sensor on a circuit board, for example.
FIG. 10 illustrates a state where the rolling element 96 is superposed on the light emitting element 95 under the pull of gravity. In this state, the light emitted by the light emitting element 95 is blocked by the rolling element 96, thereby inhibited from reaching neither of the photodetectors 94A, 94B. In the case where the tilt sensor X is inclined to the left from the state shown in FIG. 10, the rolling element 96 becomes superposed on the photodetector 94A. In this state, the light from the light emitting element 95 solely reaches the photodetector 94B. On the contrary, when the tilt sensor X is inclined to the right from the state shown in FIG. 10, the rolling element 96 becomes superposed on the photodetector 94B, in which case the light from the light emitting element 95 solely reaches the photodetector 94A. In the case where the tilt sensor X is implemented on a circuit board for example, a tilting motion of the circuit board about an axis perpendicular thereto can be detected through monitoring the photo detection signal from the pair of photodetectors 94A, 94B. Employing such tilt sensor X enables detecting, for example, a vertical or horizontal orientation of a mobile phone set by the user viewing the display screen thereof, and changing the orientation of the image on the display screen according to the orientation of the mobile phone.
The tilt sensor X thus designed is intended for detecting an orientation in the case where the tilt sensor is rotated about the axis extending in a z-direction (Ref. FIG. 9), from the state shown in FIG. 10. Accordingly, it is difficult to detect the orientation with the tilt sensor X in the case where the tilt sensor is rotated about an axis extending in an x-direction, from the state shown in FIG. 10. To utilize the tilt sensor X for more various purposes, it is preferable that the tilt sensor X is capable of detecting more diverse orientations.